The objective of this project is to design, fabricate, and test colocated earphones/microphones for use in in-ear active noise reduction (ANR) systems. Our innovation is based on a silicon micromachined membrane that serves as both the sensing element for a microphone and simultaneously the actuation surface for the earphone. By colocating the earphone and microphone, our device eliminates the acoustic phase delay between the ANR sensor and actuator, thereby enabling feedback algorithms with higher gain at higher frequency than is possible using separate devices. Current hearing protection designs provide approximately 30 dB of attenuation at the ear. This level of protection is not sufficient to allow long exposures in many industrial noise environments (which may exceed 130 dB) while maintaining the at-the-ear sound levels within prescribed safety limits. In order to keep within current NIOSH and OSHA noise exposure standards, new technologies are needed that will protect individuals from long-term exposure to harmful noise levels that could potentially result in temporary or permanent hearing threshold shifts. During the Phase I project, we will demonstrate the feasibility of our innovation by fabricating and testing prototypical devices. During Phase II, we will optimize the design, fabricate devices, and test the prototypes in in-ear ANR systems.